Neoadjuvant Pembrolizumab and Porustobart in Resectable pMMR/MSS Colon Cancer

September 3, 2026 updated by: Solstice Oncology, Inc.

A Phase 2, Open-Label, Multicenter, Randomized Trial Evaluating the Efficacy and Safety of Different Schedules of Neoadjuvant Pembrolizumab and Porustobart in Patients With Resectable pMMR/MSS Colon Cancer

The goal of this clinical trial is to learn if giving two medicines together, porustobart and pembrolizumab, before surgery can treat a common type of colon cancer called microsatellite stable (MSS) colon cancer in adults. This type of cancer can be removed with surgery and has not spread to other parts of the body. Both medicines work by helping the immune system fight cancer.

The main questions this study wants to answer:

How well do the medicines destroy the cancer before surgery? What side effects do participants have when taking the medicines?

Researchers will compare two groups to see which treatment schedule works better and is safer. Both groups get pembrolizumab. One group gets one dose of porustobart (Day 1 only), and the other group gets two doses (Day 1 and Day 22).

Participants will:

Complete certain tests and procedures to make sure they are eligible Get the medicines through a vein on Day 1 and Day 22 then have surgery 6-9 weeks after starting treatment Return for checkups and tests every 6 months for up to 3 years after surgery

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

100

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Belgium
      • Anderlecht, Belgium
        • Investigator Site
      • Bonheiden, Belgium
        • Investigator Site
      • Ghent, Belgium
        • Investigator Site
      • Leuven, Belgium
        • Investigator Site
      • Liège, Belgium
        • Investigator Site
      • Ostend, Belgium
        • Investigator Site
      • Woluwe-Saint-Lambert, Belgium
        • Investigator Site
  • Italy
      • Milan, Italy
        • Investigator Site
      • Naples, Italy
        • Investigator Site
      • Pisa, Italy
        • Investigator Site
  • Netherlands
      • Amsterdam, Netherlands
        • Investigator Site
  • Spain
      • Barcelona, Spain
        • Investigator Site
      • L'Hospitalet de Llobregat, Spain
        • Investigator Site
      • Madrid, Spain
        • Investigator Site
  • United Kingdom
      • Aberdeen, United Kingdom
        • Investigator Site
      • Cardiff, United Kingdom
        • Investigator Site
      • Glasgow, United Kingdom
        • Investigator Site
      • Leeds, United Kingdom
        • Investigator Site
      • London, United Kingdom
        • Investigator Site
  • United States
    • California
      • Los Angeles, California, United States, 90033
        • Investigator Site
    • Florida
      • Tampa, Florida, United States, 33612
        • Investigator Site
    • Illinois
      • Chicago, Illinois, United States, 60637
        • Investigator Site
    • Maryland
      • Baltimore, Maryland, United States, 21287
        • Investigator Site
    • Massachusetts
      • Boston, Massachusetts, United States, 02114
        • Investigator Site
    • New York
      • New York, New York, United States, 10016
        • Investigator Site
      • New York, New York, United States, 10021
        • Investigator Site
      • New York, New York, United States, 10027
        • Investigator Site
    • Ohio
      • Cleveland, Ohio, United States, 44106
        • Investigator Site
    • Tennessee
      • Nashville, Tennessee, United States, 37232
        • Investigator Site
    • Washington
      • Seattle, Washington, United States, 98109
        • Investigator Site

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

≥18 years of age at consent

Adenocarcinoma of the colon (rectosigmoid considered non-rectal); pMMR/MSS status

Any T3 or T4, N any, M0; disease amenable to surgical resection

ECOG Performance Status 0-1

Adequate tumor tissue sample with associated pathology report

Adequate hematologic, hepatic, and renal function

Reproductive status/contraception requirements per protocol

Exclusion Criteria:

Investigational agent within 3 weeks of first dose

Imminent or urgent need for surgery

Prior treatment with ICIs targeting CTLA-4, PD-1, or PD-L1

Systemic corticosteroid/immunosuppressive therapy within 1 week of first dose (exceptions apply)

History of severe hypersensitivity to a fully human mAb; interstitial lung disease; pneumonitis requiring corticosteroids

Active or history of autoimmune disease requiring systemic treatment within 2 years

Major surgery within 4 weeks of first dose; active infection requiring treatment

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Arm 1
Pembrolizumab IV every 3 weeks x 2 doses (Day 1, Day 22) plus porustobart x 1 dose (Day 1 only)
Drug: Pembrolizumab
Administered to: Arm 1, Arm 2
Other Names:
  • Keytruda
Drug: Porustobart
Administered to: Arm 1, Arm 2
Other Names:
  • HBM4003
Experimental: Arm 2
Pembrolizumab IV every 3 weeks x 2 doses (Day 1, Day 22) plus porustobart every 3 weeks x 2 doses (Day 1, Day 22)
Drug: Pembrolizumab
Administered to: Arm 1, Arm 2
Other Names:
  • Keytruda
Drug: Porustobart
Administered to: Arm 1, Arm 2
Other Names:
  • HBM4003

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Major Pathologic Response (MPR) rate by Blinded Independent Pathologic Review (BIPR)
Time Frame: Assessed from surgical resection specimen (surgery occurs Day 42-Day 63, i.e., approximately Week 6-Week 9 after first dose)
MPR is defined as the proportion of patients with ≤10% residual tumor volume in the primary tumor and lymph nodes, as evaluated by BIPR, per treatment arm
Assessed from surgical resection specimen (surgery occurs Day 42-Day 63, i.e., approximately Week 6-Week 9 after first dose)

Secondary Outcome Measures

Outcome Measure
Time Frame
Pathologic Complete Response (pCR) rate
Time Frame: Assessed from surgical resection specimen (Week 6-9)
Assessed from surgical resection specimen (Week 6-9)
Incidence of treatment-related adverse events (AEs), serious adverse events (SAEs), and immune-related AEs
Time Frame: From informed consent through 60 days after last dose (or initiation of new anti-cancer treatment, whichever occurs first)
From informed consent through 60 days after last dose (or initiation of new anti-cancer treatment, whichever occurs first)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Solstice Oncology, Inc.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

September 30, 2026

Primary Completion (Estimated)

September 30, 2029

Study Completion (Estimated)

September 30, 2029

Study Registration Dates

First Submitted

September 3, 2026

First Submitted That Met QC Criteria

September 3, 2026

First Posted (Actual)

September 8, 2026

Study Record Updates

Last Update Posted (Actual)

September 8, 2026

Last Update Submitted That Met QC Criteria

September 3, 2026

Last Verified

September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • SOL1-201
  • 2026-527233-58-00 (Ctis)

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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